Possible Condensation Solution?

[Tom Watson]

On some days, mostly in the Fall and the Spring, I have a problem with condensation forming on the cast iron tops of the tools, causing rust.

I use wax and I've tried Boeshield and Topcoat but there are some days, usually when the night has been pretty cool and a warm moist air mass moves in, that they are not up to the job.

I'm guessing that the cast iron has enough thermal mass that it can't respond to the change in temperature quickly enough, so that, if the humidity is high enough, the cast winds up being below the dew point and condensation forms. It's not a problem on the sheet metal.

I was wondering if it might be worthwhile to mount a ceramic base light bulb fixture inside the cabinet of the tablesaw and the shaper. I was thinking that, if I mounted it up high in the cabinet, close to the table, a sixty watt bulb would provide enough heat to keep the cast above the dew point.

Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania

[Wood Butcher]

I was thinking along the same lines Tom. In theory it should work fine but in execution the light bulb has at least 2 problems.

1. Vibration from the tool could drastically shorten the life of the bulb.
2. The wings will receive little heat from the bulb and still be subject to condensation.

So I got to thinking about using an old electric blanket intended for a bed. This could easily be draped over the whole top to heat the wings too, and is easily removable.

Art

[Tom Watson]

How about using a vibration resistant bulb like the ones used for garage door openers?

Won't the heat migrate through the cast iron sufficiently? I don't know - I'm asking.

Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania

[Bay Area Dave]

get a rough-service bulb

dave

Wood Butcher wrote:

[Jim Mc Namara]

I used a heating pad . . . worked just fine in the Houston humidity.

Jim

[William Robert]

Have you tried a ceiling fan and turning up the heat a little in the shop?

[Tom Watson]

I was thinking that it would be cheaper to heat the object, rather than heat the whole shop.

This problem usually occurs during the transition times of the year when the shop heat would not be on.

Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania

[Clint Neufeld]

Would one of the "car cover" type blankets do anything in this case? I've never had a car cool enough to worry about, but it seems to me their purpose would be to not allow the humidity to build up under them, so the precious metal underneath doesn't rust.

Clint

[Tom Watson]

I use a heating pad nearly every night - for my back.

I was thinking that the light bulb idea would be cheap and easy.

(hey - weren't them the names of those twins you went out with in high school?)

(tom assumes a defensive posture and begins to search the sky for incoming)

Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania

[Myxylplyk]

Tom, THis sounds more like a lack of insulation. Even though my shop is unheated, I did get R13 + 3/4" plywood on the walls. This holds the interior temperature and allows for a slow transition. Thus greatly reducing/eliminating condensation. Additionally, there is a lagre quantity of "stuff" in the shop adding to the thermal mass, slowing temperature transition further. I also do no open the doors or windows until mostly equilibrium is met. I have had no condensation or rust problems since insulating and staying closed up as described. (I live in upstate NY where spring and fall temps swing wildly.)

Good luck,

Myx

[Bay Area Dave]

yeah, the cast will conduct the heat just like your momma's big skillet! :)

dave

Tom Watson wrote: snip

[George]

Both good. I like a little electric heat with a fan to circulate. If a ceiling fan, might just go with one of those mineral oil thermostatic controlled types.

[admin]

Yup. you've got the physics of the situation *exactly* correct.

"Methodology sound, implementation flawed."

The bulb _inside_ the saw is likely to get broken by stuff flying around inside the cabinet. There is also a risk of sawdust accumulating _on_ the bulb, and catching fire. *NOT* a good idea.

Build a (relatively) light-weight framwork to surround the piece of equipment -- a few inches clearance on each side, and a foot or so clearance on the top. run a diagonal member across the top, so you can put a hook-eye approximately centered over the saw. Make a 'shroud' that fits over the framework, and goes at least halfway to the floor. something 'windproof' is ideal.

To use, set up the frame, hang an *incandescent* trouble-light from the hook-eye, turn it on, and put the shroud over things.

[Wood Butcher]

That may work. Better than a standard bulb anyway.

Yes it will conduct. Some. The conduction area where the wing bolts to the main tabletop is really small compared to the area the wing has to radiate heat from. Under certain temp/humidity conditions this may be ok and under others maybe not. I don't know for sure either, but I do know that the handle on a cast iron skillet can be just uncomfortably warm when while the bottom is frying sausage.

[Charlie Self]

Tom Watson responds:

Like last night and today and probably tonight? I was so wet today that I'm a bit surprised I didn't rust. Maybe that's why my joints are creaking?

Charlie Self

"I think there is a world market for maybe five computers." Thomas J. Watson

[A Dog Named Stain]

Second the electric blanket idea. Cheap, safe and you only need to set it on the lowest setting. Just push the saw and shaper together and throw the blanket over the top.

[Tom Watson]

Nah.

Let's say that the ignition temperature is in the range of 400 - 600 F and we reduce the bulb wattage to 40W, which would have a surface temperature of about 240 F.

Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania

[Rob V]

I have the same problem.

My shop is the 3rd stall of the garage. (there are 2 doors - 1 double for the main garage - and 1 single for my shop.)

Last night was so humid and this morning - it got up to about 65 pretty quickly. I came out to the shop about 9:30 and my table saw and jointer was literally dripping condensation.

I wiped it off only to show a nice coating of rust already. Im thinking of just trying a cover - but I do like that heating pad. What would be better is if I can find a temperature switch that would automatically turn it on/off when it reaches about 55 or so.

[Pounds on Wood]

I agree it won't get hot enough to be a worry, but if the bulb were to break (see the recent exploding bulb thread), whilst you were running the saw, it might be possible to cause a fire. Obviously you would just turn the bulb off while using the equipment, but "doodoo occurs".

[Tom Watson]

Because of the objections to the light bulb idea, for reasons of possible breakage, I started thinking about those little heat mats that are used for seedlings. You can get them with thermostats.

Maybe if one of these was fastened to the underside of the cast iron top it would work. It would be out of the inside of the cabinet, where it might be damaged. The thing could be left plugged in and allowed to run off the thermostat.

Regards, Tom Thomas J. Watson-Cabinetmaker Gulph Mills, Pennsylvania